This invention relates generally to valve operating mechanisms for use in internal combustion engines and, more particularly, to an oscillating rocker arm assembly and subassembly having rolling members.
Conventional valve train rocker arms of internal combustion engines use various bearing means. In addition to loads generated by the rocker arms pushing the valves against the force of the valve springs, loads are generated by the oscillating motion of the rocker arms themselves. In order to increase fuel efficiency and performance of internal combustion engines, bearings with rolling members have been used in place of plain bearings to accommodate those loads.
Typically, a rocker arm assembly with rolling members is supported on a support shaft mounted perpendicularly on a support stud extending from the head of the engine. The rocker arm is pivoted on the support shaft, which serves as an inner raceway, by means of drawn cup needle roller bearings mounted on the rocker arm. Retaining rings on the ends of the support shaft engage the cups of the bearings to limit axial movement of the support shaft relative to the rocker arm.
Other rocker arm assemblies with rolling members have been proposed which permit a support shaft and bearing subassembly to be loaded into a rocker arm from the top or from the side. However, such subassemblies require an expensive "closed" (2-bend) cup bearing and may be subject to inadvertent upside down assembly. Some such proposals may have axial "slop" of the rocker arm with respect to the support shaft.
Another problem common with previously proposed rocker arm assemblies is inadequate rigidity of the rocker arm. Rocker arms may be cast of alloy to achieve sufficient rigidity without unacceptable weight; however, such construction is expensive and impractical for many applications. Rocker arms may also be made by punching and stamping steel sheet into a cup-shaped configuration, but such rocker arms may not be sufficiently rigid for some purposes.
The foregoing illustrates limitations known to exist in present rocker arm bearing assemblies. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.